Oil and gas recovery from wells is a key technology in providing for modern energy needs. As an oil pool is depleted, the characteristics of the fluids and rock formation being accessed by the well modify with commensurate impact on the efficiency of oil harvesting. Various systems have been created to manage issues in this concern. Some systems for use in this regard are described U.S. Pat. No. 7,051,817; U.S. Pat. No. 7,147,058; and also US Patent Application 2006/0213652. All of these patents and patent applications are hereby incorporated by reference herein. The patents bring forth various interrelated issues in management of pressure, oil field reservoir characterization, entrained gas, entrained water, augmented pumping, and the like respective to the interface between the bottom hole of an oil well and the pumping system used to remove the oil.
In determining oil field reservoir status, various methods for determining petrophysical parameters (e.g., porosity) of rocks have been previously described. One traditional method tests a geologic sample of rock under atmospheric pressure to derive a porosity value. One drawback to this traditional method is that the porosity in the actual pressurized rock (under geologic pressure forces) is different than the porosity at atmospheric pressure. A further method is described by Chernikov K. A., Slavin V. I., Aristarov M. G., etc. in the Dictionary On Geology Of Oil And Gas (Bowels, 1988, 679 p.). In this second method for defining porosity, an acoustic impulse seismic evaluation of a wellbore uses the time interval between an acoustic impulse and its reflected acoustic wave to derive a porosity value for comparison with a traditionally-determined porosity value from the measured geophysical parameters for different types of rocks.
In yet another method (M. D. Belonin, V. I. Slavin, D. V. Chilingar; Abnormal Pressures. Origins, Prediction, Problems Of Development Of Hydrocarbon Fields; St. Petersburg, Nedra, 2005, 324 pp.), the depth of a deposit is factored into the porosity determination. This article brings forward the issue of effective pressure (respective to the depth of a rock formation) and its impact on the petrophysical parameter measurements respective to either irreversible deformation behaviour (at a depth effectively below a critical elastic deformation depth value) in the rock or elastic deformation (at a depth effectively shallower than the critical elastic deformation depth value).
A triaxial compression method is discussed by Sitnikov M. F., Volik A. L., and Kuksov A. K., in The Results Of The Research Of Rock Samples Deformation At Secondary Consolidation (Journal of “Drilling”, 1971. Number 9, pages 33-36). Triaxial pressure gradually compresses a sample, and a functional relationship between sample length and compression time is derived. The measured parameters are converted into, for example, permeability according to the Darcy equation. Empirical results have show an inflection point in an otherwise linear functional relationship where the rock presumably undergoes a clear structural aspect shift in density—presumably a compromise in rigidity of the supporting walls of microcavities (pores) in the rock.
One drawback of independently-administered methods is that interdependences respective to permeability, porosity, and fluid flow are not defined during the method implementation and thereby do not provide a comprehensive predictor of fluid flow characteristics. Existing methods also tend to achieve the best results for simple carbonate and clastic rocks, which are insignificantly fractured. What is needed is a method and system for fully defining petrophysical parameters (permeability, porosity and the like) of a broad spectrum of rocks (simple carbonate and clastic rocks and complex fractured carbonate and clastic rocks) under influence of effective pressure at both irreversible and elastic deformation depths. Another need is for rapid determination of permeability status of geological structure samples in an operating oil well.